Beschreibung:
<label>Abstract</label>
<p>This study analysed the contribution of each omega-3 desaturase to the cold response in soybean. Exposure to cold temperatures (5 °C) did not result in great modifications of the linolenic acid content in leaf membrane lipids. However, an increase in the<italic>GmFAD3A</italic>transcripts was observed both in plant leaves and soybean cells whereas no changes in<italic>GmFAD3B</italic>or<italic>GmFAD3C</italic>expression levels were detected. This increase was reversible and accompanied by the accumulation of an mRNA encoding a truncated form of<italic>GmFAD3A</italic>(<italic>GmFAD3A-T</italic>), which originated from alternative splicing of<italic>GmFAD3A</italic>in response to cold. When the expression of plastidial omega-3 desaturases was analysed, a transient accumulation of<italic>GmFAD7-2</italic>mRNA was detected upon cold exposure in mature soybean trifoliate leaves while<italic>GmFAD7-1</italic>transcripts remained unchanged. No modification of the<italic>GmFAD8-1</italic>and<italic>GmFAD8-2</italic>transcripts was observed. The functionality of<italic>Gm</italic>FAD3A,<italic>Gm</italic>FAD3B,<italic>Gm</italic>FAD3C and<italic>Gm</italic>FAD3A-T was examined by heterologous expression in yeast. No activity was detected with<italic>Gm</italic>FAD3A-T, consistent with the absence of one of the His boxes necessary for desaturase activity. The linolenic acid content of<italic>Sacharomyces cerevisiae</italic>cells overexpressing<italic>Gm</italic>FAD3A or<italic>Gm</italic>FAD3B was higher when the cultures were incubated at cooler temperatures, suggesting that reticular desaturases of the<italic>Gm</italic>FAD3 family, and more specifically<italic>Gm</italic>FAD3A, may play a role in the cold response, even in leaves. The data point to a regulatory mechanism of omega-3 fatty acid desaturases in soybean affecting specific isoforms in both the plastid and the endoplasmic reticulum to maintain appropriate levels of linolenic acid under low temperature conditions.</p>